Machine for grooving brake blocks

ABSTRACT

Machine and method for providing criss-cross grooves in the concave face of precurved brake block forms. A precurved brake block from is located with its radii intersecting along a line to define an axis about which the block is swung and advanced linearly therealong in a direction to define a helical path. While traversing the helical path the concave face of the block passes a set of cutters which score the face thereof with a plurality of parallel grooves disposed at a helical angle with respect to the block. The direction of axial advance is then reversed and the concave face of the block passes a second set of cutters which score the face thereof with other parallel grooves which cross the first grooves in a criss-cross pattern.

[ 51 Apr.3, 1973 [54] MACHINE FOR GROOVING BRAKE BLOCKS [75] Inventor: Carl Edward Gillberg, North P1ainfield, NJ.

[73] Assignee: Johns-Manville Corporation, New

York,N.Y.

22 Filed: Aug.30, 1971 21 Appl.No.: 176,156

[52] US. Cl. ..90/1l C, 90/1l.42, 90/11.62, 90/1 1.48, 90/l1.46, 90/20, 82/4 A, 83/7,

[51] Int. Cl ..B23c 3/34 [58] Field of Search.....90/ll C, 11.42, 11.62, 11.64, 90/20, 11.46, 11.48; 82/4 A, 4 D, DIG. 3;

[56] References Cited UNITED STATES PATENTS 1,933,362 10/1933 Bergstrom ..90/11.46

jOZ

2,330,921 10/1943 Rickenmann ..90/20 Primary Examiner- Francis S. Husar Attorney-John A. McKinney et a1.

[57] ABSTRACT Machine and method for providing criss-cross grooves in the concave face of precurved brake block forms. A precurved brake block from is located with its radii intersecting along a line to define an axis about which the block is swung and advanced linearly therealong in a direction to define a helical path. While traversing the helical path the concave face of the block passes a set of cutters which score the face thereof with a plurality of parallel grooves disposed at a helical angle with respect to the block. The direction of axial advance is then reversed and the concave face of the block passes a second set of cutters which score the face thereof with other parallel grooves which cross the first grooves in a criss-cross pattern.

16 Claims, 29 Drawing Figures PATENTEDAPR 3 mm SHEET 1 [IF 6 PATENTEDAPRS 191s SHEET 3M6 PATENTEDAPRIS I975 3,724'327 SHEET u 0F 6 PATENTEDAPR 3 1973 SHEET 5 BF 6 MACHINE FOR GROOVING BRAKE BLOCKS BACKGROUND OF THE INVENTION This invention relates to a machine and method for providing helical grooves in the concave face of precurved brake block forms. The brake blocks are held inside a drum which is revolved in a helical path to bring the brake block into contact with rotating cutters. Sets of parallel grooves one having a right hand and the other having a left hand helical direction are cut into the surface of the concave face as it passes across respective rotating cutters at two stations in the cycle, whereby a criss-cross pattern is obtained.

Criss-cross grooves have long been provided on the concave face of curved brake blocks for the purpose of providing paths for cooling fluid to circulate between the block and drum. The paths also provide for air or oil to enter adjacent the face for obtaining quick release from a brake drum.

One method of providing grooves in the interface (concave face) of a brake block or liner has been to cut the grooves in the face of the material while it is in flat form, and thereafter curve the material to the required radius. This is not economical because it requires the brake block material to be processed in at least two stages. Practically all brake blocks include in the formula a cement which, when cured, causes the block to assume a mechanically rigid form. The grooves are provided by previously known methods in the incompletely cured flat material and thereafter, prior to curing, bent to the desired radius. Grooving was performed in this manner because no economical way has been successfully devised to provide helical grooves of crisscrossing pattern on a precurved concave cylindrical surface.

In the present invention, the brake block is preformed and cured in a rigid body having a desired radius. Thereafter, the brake block is indexed and held inside a revolving drum with its concave face directed inwardly while revolved or swung in a helical path across cutters in a manner to provide the desired helical grooves of different hand direction in the concave surface thereof to define the criss-cross pattern.

Brief Summary of the Invention It is an object of this invention to disclose a method of providing grooves in the concave face of precurved brake blocks;

It is another object of this invention to disclose a method of providing criss-cross grooves in the concave face of precurved brake blocks wherein the blocks are carried in a helical path past revolving cutters;

It is an object of this invention to disclose a machine capable of providing grooving in the concave face of a precurved brake block.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and further objects and advantages thereof will become apparent when reference is made to the following detailed description of the preferred embodiment of the invention and the accompanying drawings in which:

FIG. 1 is a side elevation of the brake block grooving machine;

FIG. 2 is a plan view of the machine;

FIG. 3 is an end elevation of the machine, but showing only certain parts thereof;

FIG. 4 is an end elevation of the drum and discharge trough;

FIG. 5 represents a development of the surface of a cam of the machine;

- FIG. 6a is a schematic illustration of a portion of the machine in side elevation in the upright loading position, i.e., 0 position;

FIG. 6b is the same as FIG. 6a but with the cam and drum rotated to the 90 position;

FIG. illustrates the cam and drum rotated to the 180 position;

FIG. 6d illustrates the cam and drum rotated to 270 position;

FIG. 6e illustrates the cam and drum rotated to the 360 position, i.e., the unloading position, the same position as illustrated in FIG. 6a;

FIG. 7a represents an end view of the drum shown to its left in FIG. 6a at loading position, i.e., 0 position;

FIG. 7b represents an end view of the drum when rotated to the 90 position;

FIG. represents an end view of the drum when rotated to the 180 position;

FIG. 7d represents an end view of the drum when rotated to the 270 position;

FIG. 7e represents an end view of the drum when rotated to the 360 position, i.e., the unloading position;

FIG. 8a represents the outline of a precurvedbrake block as carried by the drum with its concave surface facing the viewer;

FIG. 8b represents the outline of the same brake block described in FIG. 8a when rotated by the drum to the 90 position wherein grooves are being cut;

FIG. represents the same brake block when rotated to the 180 position;

FIG. 8d represents the same brake block when rotated to the 270 position;

FIG. 8e represents the same brake block when rotated to the 360 position, having completed one revolution or cycle;

FIG. 9 is a sectional elevation taken through the magazine containing a stack of ungrooved precurved brake blocks and showing the loading bars in a retracted position;

FIG. 10 is an end view of the magazine;

FIG. 11 is another sectional elevation of the magazine wherein the loading bars have carried a brake I block partially toward the drum;

FIG. 12 is similar to FIG. I but shows the loading bars having advanced into the drum with the brake block at the 0 position, i.e., loading station;

FIG. 13 is an elevation view of the drum partially cut away to illustrate a cutter in the process of cutting parallel grooves in the block at the position;

FIG. 14 is an elevation view of the drum partially cut away to illustrate another cutter in the process of cutting additional parallel grooves in the block at the 270 position;

FIG. 15 is an enlarged end view of the drum and mechanism for holding the curved brake block in indexed position;

FIG. 16 represents the concave face of the brake block showing grooves disposed in criss-cross pattern; and

FIG. 17 is a side view of the block shown in FIG. 16.

The object of the machine is to move a precurved molded brake block form past a plurality of revolving cutters at plural stations so as to score the concave face thereof by a plurality of helically disposed parallel grooves. The machine, identified generally by the numeral 10, is comprised of several parts each performing a cooperating function. For purposes of clarity in describing the machine and its operation, numerals are applied to various components generally as follows: numerals under 100 identify the frame and other miscellaneous parts; numerals in the 100 series identifying the main shaft, bearings and rotating drum; numerals in the 200 series identifying the driving motor and power train; numerals in the 300 series identifying the cam; numerals in the 400 series identifying the brake block feed magazine, loading rods and other mechanism; and numerals in the 500. series identify the rotating cutters and their driving motors.

Frame 12, adapted to be supported from a floor or foundation carries the various components. Projecting above frame 12 is a pair of upstanding platforms 13 and 13' which mount, respectively, bearings 102 and 102'. See FIG. 1. Additional platforms 15 and 15 are located at the other end of the frame for carrying cutters and their drive mechanism.

As illustrated in FIG. 1, bearing 102 and 102' rotatably carry shaft 104 therethrough. A portion of this shaft is provided with longitudinal splines which are received within splined sleeves 106 and 106' (not fully shown) which are rotatably mounted in bearings 102 and 102'. The splines permit the shaft to move longitudinally as well as rotationally in the bearings. Shaft 104 is rotatably driven by internally splined sprocket 206, which in turn is driven through chain 208 from gear reduction unit 212. Electrical motor 210, FIG. 2, drives through selectively operated combination electric clutch and brake mechanism 214 to power gear reduction unit 212.

Cam 302, secured to shaft 104, includes a groove track 304 about its periphery. A cam follower 306, which is adjustably fixed with respect to the frame, is received within the groove track 304. As the groove follows over cam follower 306, cam 302, shaft 104 and drum 106 follow a reciprocating path. As the drum revolves through 360, it also moves in a helical path. The drum is adapted to receive a precurved brake block in indexed position internally thereof and move it in two passes across revolving cutters. This operation will be described later in the specification.

Electric motor 210 operates continuously, and at selected intervals electric clutch 214 (FIG. 2) is energized for driving through gear reduction unit 212 to rotate sprocket 216, sprocket 206 and shaft 104. The clutch is energized at one time sufficiently long for permitting drum 106 to make one complete revolution. The grooved brake block is removed from the drum and a new (ungrooved) block is inserted into the drum whereupon another 360 cycle is commenced. The operation will be more fully disclosed hereinafter with particular reference to other figures of the drawing.

Brake block feed magazine and loading mechanism, generally identified by the numeral 400, is mounted above the frame and generally to one side of drum 106, see FIGS. 1 and 2. Magazine 402 comprises a pair of spaced apart plates 404 and 406 adapted to receive a stack of precurved brake blocks therebetween. Also see FIG; 10 which shows an end view of the magazine. The magazine is filled from the top, and the precurved block so stacked therein rest on reduced diameter extensions of rods 408 and 408'. These extensions are adapted to carry one ungrooved block into drum 106 where it is indexed into position and there retained by clamping means. This detail will be more fully disclosed hereinafter with reference to other figures of the drawings.

Rods 408 and 408 are supported above plate 410 which is adapted to slide longitudinally between guides or ways 412 and 414. The ways are supported from a frame 416 fixedly carried from frame 12 above bearings 102, 102. A block 418, upstanding from plate sliding 410, is adapted to be connected to cable 419, which is disposed over spaced apart pulleys 420 and 420'. This cable is connected to the plunger or air cylinder 422 for movement therewith. Upon operation of the air cylinder plate 410 is caused to move, thereby carrying rods 408, 408' in either direction. As the rods move to the right, as shown in FIGS. 1, 9, 11 and 12, they carry an ungrooved brake block from the bottom of magazine 402 into position in drum 106. After the block has been clamped into indexed position, rods 408, 408' are withdrawn toward the left out of the drum to the position shown in FIGS. 1 and 9. Thereafter, rotation of drum 106 may commence.

As illustrated in FIGS. 1 and 2, a pair of motors 502 and 504 drive respective cutter heads 506 and 508, in counterclockwise directions as viewed from the rear of motors 502 and 504.

The cutter heads are each disposed inside the drum near the inside periphery thereof and at an angle thereto. The cutters may be positioned by adjustment mechanism generally identified by the numeral 526. Motor 502 and 504 are mounted on plates 528 and 530 respectively which are adapted to be held by a backing member 532 and 534 in a plurality of angular positions. This angular adjustment coupled with additional movement of motors 502, 504 in three directions by screw adjustments represented by cranks 536 and 538 for vertical position; cranks 540 and 542 for horizontal adjustment; and, cranks 544 and 546 for longitudinal adjustment are adapted to position the cutting heads in any desired position.

Each cutter head 506, 508 is comprised of a plurality of toothed discs axially spaced apart on shafts 510, 512. This discs at each end of the head are of a smaller diameter than the discs located in the center. This permits the cutters to have an overall contour which generally coincides with the concave face of the brake block which advances past the cutter head on a helical path.

A discharge chute is shown in FIGS. 1, 2 and 4 for the purpose of receiving the finished grooved block when it is ejected from drum 106. The chute is adapted for selective positioning. As shown in FIG. 4, it is raised to an elevated position above and out of the way of rotating drum 106 during the cutting operation (i.e., grooving of brake block), and is lowered for receiving the finished block which is ejected from the end of the drum. As the chute is again elevated the finished (grooved) block slides down the incline thereof and off the end for collection in a receptacle (not shown). The

raising and lowering of chute 120 is accomplished by a selectively operated air cylinder 122. Cutter heads 506 and 508 and driving motors 502 and 504 are not shown in FIG. 3 in order to illustrate an end view of drum 106 and adjustment mechanism 526 more clearly.

Drum 106 comprises a cylindrical shell mounted to end plate 108 carried by shaft 104. A portion 110 of end plate 108 is cut away to allow a brake block to be carried from magazine 402 into position within the drum. A segment is cut out of the periphery of drum 106 for the purpose of mounting clamp mechanism to receive a precurved brake block. End sectional view il' lustrated in FIG. shows the mounting mechanism most clearly. The cut out portion of the periphery of drum 106 amounts to approximately a 30 segment. Mounted within the cut out segment is holding mechanism 128 for receiving and clamping a brake block 50 in proper position during the grooving operation. Each size brake block requires a corresponding size holding mechanism.

As shown in FIG. 15, arched plate 130 underlies the segmental opening in drum 106. This plate is disposed on a constant radius from the axis of the drum and is spaced inwardly from the drum periphery by the thickness of spacer bars 132 and 134 located on op posite sides thereof. These bars extend generally along the entire longitudinal extent of the drum, while plate 130 extends only about half way, see FIG. 2. Plural cap screws 131 extend through spacer bars 132, 134 into plate 130 for holding the plate in position. Located on the convex side of plate 130 is a pair of upstanding lugs 136 which by a cross pin therethrough support the end of piston rod 138 of cylinder 140. The other end of the cylinder is pivotally connected to a pawl 142 pivotally carried by pin 143 anchored to spacer block 134. A portion of pawl 142 terminates below plate 130.

Cylinder 140 includes a coil spring internally thereof for urging plunger 138 to extended position. Since lugs 136 are fixed, a clockwise bias is applied to pawl 142.

When the pawl is to be moved in a counterclockwise direction, an air cylinder 144 is energized so that piston 146 moves to the left for moving it counterclockwise. Upon return of the air cylinder to its retracted position, the pawl is again urged to its normal clockwise or holding position.

Brake block 50 nests against the concave face of plate 130 and is held in position thereagainst by being urged against shoulder 148 by the action of pawl portion 148 which extends below plate 130. As long as tension of pawl 142 is applied against block 50, the block is held in the position shown in FIG. 15. Whenever the spring tension on the pawl is overridden, block 50 can be removed. Removal of grooved block 50 is accomplished by being ejected endwise by the insertion of another block.

For each size brake block, such as variations in length, width or radius, a different holding mechanism 128 is required having a corresponding concave face and shoulder location. The radius of the brake block to be grooved determines the thickness required for spacer blocks 132 and 134. It will be readily apparent that if a brake block having a radius shorter than block 50, shown in FIG. 15, is to be grooved, the block will need to be held at a shorter distance from the center of the drum. Spacer blocks 132 and 134 would be replaced by correspondingly thicker blocks.

Reference has been made to the positioning of cutter heads 506 and 508 relative to drum 106. As illustrated in FIGS. 13 and 14, the cutters are respectively positioned at 20 and 22-30' relative to the horizontal. The cutting heads and drive motors can be selectively positioned in three dimensions as indicated by the adjusting mechanism illustrated in FIGS. 1, 2, and 3. It is necessary that each cutter head be somewhat longer than the width of a block to be grooved because the block passes thereover in a helical path as illustrated in FIGS. 13 and 14.

A finished brake block is illustrated in FIGS. 16 and 17 wherein parallel grooves have been cut in its concave face in a criss-cross pattern. One set of parallel grooves 52 are disposed at 20 with respect to a reference line while the other set of parallel grooves 54 are disposed at 2230' in the other direction from the same reference line. This pattern may be varied by a combination of positioning the cutter heads and selection of a cam 302 having the desired pitch in groove 304. Of course, whenever the physical dimension of the brake block itself changes, corresponding changes are required in holding mechanism 128.

Drive motor 504 and shaft are disposed at 20 above the horizontal (see FIG. 13). Groove 304 is provided with a pitch which is adapted to advance drum 106 along a helical path so that any point thereon advances along a helix. As brake block 50 passes over cutter head 508, parallel grooves 52 at 20 are cut therein. The other set of parallel grooves 54 are cut in much the same manner. Drive motor 502 and its shaft are disposed at 22-30' above the horizontal (see FIG. 14). Groove 304 is provided with a pitch on the other half of cam 302 adapted to advance drum 106 along a helical return path so that any point thereon moves along a 22-30 helix. As brake block 50 passes over cutter head 502 on the return travel, parallel grooves 54 at 22-30 are cut therein.

The precise angular relationship of the groove pattern is described for purposes of illustration to meet a particular specification. The pattern can be varied by changing cam 106 and making a corresponding change in the angleof the cutters. Regardless of the groove pattern, if the physical dimensions of the brake block change, a change in holding mechanism 128 is also required.

For cutting grooves of various patterns on a range of brake blocks, it will be necessary to carry an assortment of holding mechanisms 128 for attachment to drum 106 as well as cams 302 having grooves with appropriate pitch. Numerous combinations can be made.

An air cylinder 170, having a plunger 172, is adapted to be selectively energized to extend the plunger for engagement with a notch provided in the rim portion of end plate 108. See FIG. 2. The purpose of the engagement is to index the drum in the brake block receiving position, i.e., at the 0 position, Each cycle begins and ends with plunger 172 projecting into the notch. The notch can be located anywhere about the periphery of the drum end just so that the drum is in the 0 position when the engagement is made.

Electrical and pneumatic controls are not described in detail in this specification. Controls such as a timer, solenoids, and switches function in a known manner and the sequence of operation is determined to meet the particular machine.

The various components of this brake block grooving machine and their function have been shown and described. Description will now be made on the actual operation of the machine through one cycle as grooves are cut in the concave face of a precurved block.

OPERATION Starting with drum 106 in the position, as shown in FIGS. 1 and 2, wherein a cycle has just been completed and the freshly grooved block 50 still held clamped in position, a complete cycle will be described wherein grooves are cut in the next block.

Assuming that driving motor 210 and cutter motors 502, 504 are running continuously the following steps occur in sequence to cut grooves in the next brake block:

1. Plunger 172 is in engagement with a recess or notch on the periphery of drum 106 for indexing the drum in the 0 position for loading.

2. Air is admitted to air cylinder 422 for extending rods 408,408 longitudinally to the right, as viewed in FIGS. 1, 2, 9, 11 and 12.

3. Brake block 50 in magazine 402, which rests on reduced portions of rods 408 and 408, is carried to the right as shown in FIGS. 11 and 12.

4. As brake block 50 is carried to the station already occupied by the freshly grooved block, air cylinder 144 is actuated for extending plunger 146 into engagement with pawl 142 (FIG. for releasing engagement of portion 148 from the brake block already in position.

5. As rods 408, 408' move to the right to the position represented in FIG. 12, ungrooved block 50 is received in the position shown in FIG. 15 and the grooved block is displaced into chute 120. Chute 120 is raised by air cylinder 122 to pivot it about pin 123 to a steeper angle to cause the grooved block to slide down to a receptacle (not shown).

6. Plunger 146 then disengages from pawl 142 and the pawl is again urged clockwise by spring action in cylinder 140 for holding engagement on brake block 50.

7. Rods 408, 408' are withdrawn to the position shown in FIGS. 1, 2 and 9. Plunger 172 is withdrawn from engagement with the drum.

8. Drum 106 is now loaded and ready for rotation to carry block 50 past cutters 508 and 506 in sequence. This is illustrated as the 0 position in FIGS. 5, 6a, 7a and 8a.

9. Clutch 214 is engaged so that motor 210 drives through the train for slowly rotating shaft 104 clockwise as viewed from the right hand side of the machine in FIG. 1.

l0. Shaft 104, cam 302 and drum 106 rotation together. 11. When cam 302 is rotated past about 45 an incline portion of cam groove 304 is brought into position against fixed cam follower 306.

12. Thereafter, upon continued rotation, cam 302 is caused to have an axial component of motion which is also imparted to shaft 104.

13. Since shaft 104 is adapted for axial movement as well as rotation in bearings 102, 102, the cam, shaft and drum are rotated along a helical path as drum 106 is passing through the 90 position.

14. Helical motion of the drum (and brake block 50) continues past the 90 position.

15. In the meantime brake block 50 has been moved past revolving cutter head 508 on a helix and a plurality or parallel grooves 52 are cut in the concave face thereof. The grooves are disposed at 20 with respect to the longitudinal extent of the brake block. 1

16. From about the position to the 225 position, groove 304 is not inclined and drum 106 has only rotational motion. Note the position illustrated in FIG. 8c.

17. Commencing at about 225 of rotation, a second incline portion of cam groove 304 is brought into position against fixed cam follower 306.

18. This incline causes drum 106 to follow a helical path in the other longitudinal direction. Note in FIG. 6d that the cam, shaft and drum 106 is commencing to move back to the left.

19. As brake block 50 is moved past cutter head 506, a plurality of parallel grooves 54 are cut into the concave face thereof. These grooves, at 22-30' with respect to the longitudinal extent of brake block 50, are disposed across the grooves 52 to define a criss-cross pattern as illustrated in FIG. 16.

20. Rotation of drum 106 continues to the 360 position.

21. At this position plunger 172 once again extends for engagement with the recess on drum 106 and the cycle is complete. Only upon seating of plunger 172 are certain electrical circuits completed, thereby insuring that the drum is in the 360 position (or the 0 position) and ready for receiving another ungrooved block.

22. Another cycle now commences automatically and carries through the steps just described.

23. Each cycle takes about 6 to 10 seconds.

24. The finished block is. illustrated in FIGS. 16 and The depth of the grooves provided in the block face can be varied by adjustment on control handles 546 and 548. Mechanism and the steps for providing grooves in the concave face of a precurved rigid brake block of a certain size have been described. As the dimensions and shape of the block vary so must certain parts of the machine, e.g., the device for holding the brake block and cams having the correct incline groove. The latter, of course, determines the angle at which the grooves are cut in the block.

The mechanism may be varied in parts and still remain within the spirit of the invention. The invention is defined by the claims which follow hereafter.

I claim:

1. The method of providing helically disposed grooves in a concave face of a precurved brake block form comprising:

locating the block with its concave face directed toward an axis.

swinging the block along a portion of a helical path in both hand directions at a radius from the axis corresponding to the radii of the concave face and past cutters in each direction in interference with the concave face so that grooves are cut therein.

2. The method according to claim 1 wherein the brake block concave face is provided with one set of grooves as the block is moved in one helical path and is provided with another set of grooves as the block is moved in another helical path.

3. The method according to claim 1 wherein parallel grooves are provided as the block moves in each helical path.

4. The method according to claim 2 wherein parallel grooves are provided as the block moves in each helical path.

5. The method according to claim 3 wherein said sets of parallel grooves criss-cross each other.

6. The method according to claim 4 wherein said sets of parallel grooves criss-cross each other.

7. The method according to claim 5 wherein the brake block form is swung in one rotational direction during its movements in both helical paths.

8. The method according to claim 1 wherein said grooves are cut entirely across the face of the brake block.

9. The method according to claim 8 wherein said grooves are cut in parallel sets which criss-cross one another.

10. The method of providing grooves in a concave face of a preformed brake block form comprising:

locating the preformed brake block with its concave face at a distance from an axis corresponding to the radii of the concave face,

moving the block along a helical path in one direction past cutters for providing parallel helical grooves of one hand in the concave face thereof then moving the block along a helical path in the reverse direction past cutters for providing additional parallel helical grooves of the reverse hand in the concave face thereof which grooves crisscross the first mentioned helical grooves.

11. The method of providing grooves in a concave I face of a precurved brake block form comprising:

swinging the block in one direction about an axis defined by the intersection of radii of the concave face of the brake form,

moving the block in one axial direction while swinging so that it traverses a helical path of one hand with the concave face moving past cutting means for cutting parallel helical grooves therein,

reversing the axial direction of movement while still swinging the block in the same direction so that it traverses a helical path of a reverse hand with the concave face moving past additional cutting means for cutting parallel grooves therein of another hand.

12. The method of grooving the concave face of a precurved brake block form comprising:

securing the block to means for swinging the block through a 360 cycle at a constant radius from an axis corresponding to the radius of the concave face,

advancing the swinging means in one axial direction through a first part of the cycle and then reversing its axial direction during the latter part of the cycle so as to define out and return helical paths for the brake block form,

moving the concave face of the brake block form into cutting interference with gang cutters during each part of the cycle so as to provide plural sets of helically disposed parallel grooves of different hand in the face thereof which lie across each other to define a criss-cro ss pattern 13. A machine for providing helically disposed grooves in a concave face of precurved brake block form comprising:

frame means,

rotatable means mounted on the frame means and having a receiving station for selectively holding a brake block of arcuate form with its concave face directed toward the axis of the rotatable means at a distance from the axis corresponding to the radii of the concave face,

means for selectively rotating the rotatable means about its axis for one cycle,

means causing the rotatable means to move axially during one portion of the cycle so as to carry the concave face along a portion of a helical path of one hand direction,

said means further causing the rotatable means to move in the reverse axial direction during another portion of the cycle so as to carry the concave face along a portion of a helical path of the reverse hand direction,

gang cutters disposed in the paths of the brake block face during said movements so as to cut sets of parallel helically disposed grooves in the concave face of the brake block of opposite hand directions so that they criss-cross each other.

14. The invention according to claim 13 wherein the cutter means comprises a plurality of axially spaced apart disc-shaped cutters aligned for cutting helically disposed parallel grooves in the concave face of the brake block at the same pitch as the pitch of the helical path along which the concave face moves.

15. A machine for providing helically disposed parallel grooves which overlie each other in a criss-cross pattern in the concave face of a precurved brake block in the form of a cylindrical section comprising:

means for receiving an arcuate brake block for swinging the brake block through one revolution with the concave face directed toward the axis of revolution,

said means advancing in one axial direction during the first part of the revolution so as to traverse a helical path in one directional hand for moving concave face past gang cutters for cutting parallel helically disposed grooves in the concave face thereof,

said means thereafter advancing in the reverse axial direction during the latter part of the revolution so as to traverse a helical path in the other directional hand for moving the concave face past other gang cutter for cutting additional parallel helically disposed grooves in the concave face thereof which criss-cross thefirst provided grooves.

16. The invention according to claim 15 wherein cam means cause said swinging means to move in the axial directions. 

1. The method of providing helically disposed grooves in a concave face of a precurved brake block form comprising: locating the block with its concave face directed toward an axis. swinging the block along a portion of a helical path in both hand directions at a radius from the axis corresponding to the radii of the concave face and past cutters in each direction in interference with the concave face so that grooves are cut therein.
 2. The method according to claim 1 wherein the brake block concave face is provided with one set of grooves as the block is moved in one helical path and is provided with another set of grooves as the block is moved in another helical path.
 3. The method according to claim 1 wherein parallel grooves are prOvided as the block moves in each helical path.
 4. The method according to claim 2 wherein parallel grooves are provided as the block moves in each helical path.
 5. The method according to claim 3 wherein said sets of parallel grooves criss-cross each other.
 6. The method according to claim 4 wherein said sets of parallel grooves criss-cross each other.
 7. The method according to claim 5 wherein the brake block form is swung in one rotational direction during its movements in both helical paths.
 8. The method according to claim 1 wherein said grooves are cut entirely across the face of the brake block.
 9. The method according to claim 8 wherein said grooves are cut in parallel sets which criss-cross one another.
 10. The method of providing grooves in a concave face of a preformed brake block form comprising: locating the preformed brake block with its concave face at a distance from an axis corresponding to the radii of the concave face, moving the block along a helical path in one direction past cutters for providing parallel helical grooves of one hand in the concave face thereof then moving the block along a helical path in the reverse direction past cutters for providing additional parallel helical grooves of the reverse hand in the concave face thereof which grooves criss-cross the first mentioned helical grooves.
 11. The method of providing grooves in a concave face of a precurved brake block form comprising: swinging the block in one direction about an axis defined by the intersection of radii of the concave face of the brake form, moving the block in one axial direction while swinging so that it traverses a helical path of one hand with the concave face moving past cutting means for cutting parallel helical grooves therein, reversing the axial direction of movement while still swinging the block in the same direction so that it traverses a helical path of a reverse hand with the concave face moving past additional cutting means for cutting parallel grooves therein of another hand.
 12. The method of grooving the concave face of a precurved brake block form comprising: securing the block to means for swinging the block through a 360* cycle at a constant radius from an axis corresponding to the radius of the concave face, advancing the swinging means in one axial direction through a first part of the cycle and then reversing its axial direction during the latter part of the cycle so as to define out and return helical paths for the brake block form, moving the concave face of the brake block form into cutting interference with gang cutters during each part of the cycle so as to provide plural sets of helically disposed parallel grooves of different hand in the face thereof which lie across each other to define a criss-cross pattern.
 13. A machine for providing helically disposed grooves in a concave face of precurved brake block form comprising: frame means, rotatable means mounted on the frame means and having a receiving station for selectively holding a brake block of arcuate form with its concave face directed toward the axis of the rotatable means at a distance from the axis corresponding to the radii of the concave face, means for selectively rotating the rotatable means about its axis for one cycle, means causing the rotatable means to move axially during one portion of the cycle so as to carry the concave face along a portion of a helical path of one hand direction, said means further causing the rotatable means to move in the reverse axial direction during another portion of the cycle so as to carry the concave face along a portion of a helical path of the reverse hand direction, gang cutters disposed in the paths of the brake block face during said movements so as to cut sets of parallel helically disposed grooves in the concave face of the brake block of opposite hand directions so that they criss-cross each other.
 14. The invention according to cLaim 13 wherein the cutter means comprises a plurality of axially spaced apart disc-shaped cutters aligned for cutting helically disposed parallel grooves in the concave face of the brake block at the same pitch as the pitch of the helical path along which the concave face moves.
 15. A machine for providing helically disposed parallel grooves which overlie each other in a criss-cross pattern in the concave face of a precurved brake block in the form of a cylindrical section comprising: means for receiving an arcuate brake block for swinging the brake block through one revolution with the concave face directed toward the axis of revolution, said means advancing in one axial direction during the first part of the revolution so as to traverse a helical path in one directional hand for moving concave face past gang cutters for cutting parallel helically disposed grooves in the concave face thereof, said means thereafter advancing in the reverse axial direction during the latter part of the revolution so as to traverse a helical path in the other directional hand for moving the concave face past other gang cutter for cutting additional parallel helically disposed grooves in the concave face thereof which criss-cross the first provided grooves.
 16. The invention according to claim 15 wherein cam means cause said swinging means to move in the axial directions. 